The Scroll Up Bar - The Usability Post
▻http://usabilitypost.com/2014/05/24/the-scroll-up-bar
An interesting way to solve the issue is to hide the bar when scrolling down, and show it when scrolling up. On mobile interfaces, where space is precious, this technique is used to hide chrome, such as Web browser controls, but it’s also a good pattern to use on the Web. For example, Medium has just updated their new navigation bar. As you scroll down, the bar goes away, but it can be revealed at any time by scrolling up.